Study of abnormal vertical emittance growth in ATF extraction line

M. Alabau Pons (1, 2) , A. Faus-Golfe (2) , P. Bambade (1) , J. Brossard (1) , G. Le Meur (1) , Cécile Rimbault (1) , F. Touze (1) , R. B. Appleby , A. Scarfe , D. Angal-Kalinin (3) , J. Jones (3) , M. Woodley (4) , G. White (1, 4) , S. Kuroda , F. Zimmermann (5)

1 LAL - Laboratoire de l'Accélérateur Linéaire
2 IFIC - Instituto de Fisica Corpuscular
3 ASTEC - Accelerator Science and Technology Centre
4 SLAC - SLAC National Accelerator Laboratory
5 CERN - European Organization for Nuclear Research

Since several years, the vertical beam emittance mea- red in the Extraction Line (EXT) of the Accelerator Test Facility (ATF) at KEK, that will transport the electron beam from the ATF Damping Ring (DR) to the future ATF2 Final Focus beam line, is significantly larger than the emittance measured in the DR itself, and there are indications that it grows rapidly with increasing beam intensity. This long- standing problem has motivated studies of possible sources of this anomalous emittance growth. One possible contri- bution is non-linear magnetic fields in the extraction region experimented by the beam while passing off-axis through magnets of the DR during the extraction process. In this pa- per, simulations of the emittance growth are presented and compared to observations. These simulations include the effects of predicted non-linear field errors in the shared DR magnets and orbit displacements from the reference orbit in the extraction region. Results of recent measurements using closed orbit bumps to probe the relation between the extraction trajectory and the anomalous emittance growth are also presented.

Domaines: Physique des accélérateurs [physics.acc-ph]; Instrumentations et Détecteurs [physics.ins-det]

M. Alabau Pons, A. Faus-Golfe, P. Bambade, J. Brossard, G. Le Meur, et al.. Study of abnormal vertical emittance growth in ATF extraction line. Particle Accelerator Conference (EPAC08), Jun 2008, Genoa, Italy. pp.553-555. ⟨in2p3-00308510⟩